/*
 * The MIT License
 * 
 * Copyright (c) 2011 Takahiro Hashimoto
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.taobao.top.link.embedded.websocket.frame;

import java.nio.ByteBuffer;
import java.util.EnumMap;
import java.util.EnumSet;

import com.taobao.top.link.embedded.websocket.BufferManager;
import com.taobao.top.link.embedded.websocket.exception.WebSocketException;

/**
 * The Class FrameParser.
 *
 * @author Takahiro Hashimoto
 */
public abstract class FrameParser {

  /**
   * The Enum State.
   *
   * @author Takahiro Hashimoto
   */
  enum State {

    /** The HEADER. */
    HEADER,
    /** The FRAME. */
    FRAME,
    /** The DONE. */
    DONE;

    /** The state map. */
    private static EnumMap<State, EnumSet<State>> stateMap = new EnumMap<State, EnumSet<State>>(State.class);
    static {
      stateMap.put(HEADER, EnumSet.of(State.FRAME));
      stateMap.put(FRAME, EnumSet.of(State.DONE));
      stateMap.put(DONE, EnumSet.of(State.HEADER));
    }

    /**
     * Can transition to.
     *
     * @param state
     *          the state
     * @return true, if successful
     */
    boolean canTransitionTo(State state) {
      EnumSet<State> set = stateMap.get(this);
      if (set == null)
        return false;
      return set.contains(state);
    }
  }

  /**
   * Transition to.
   *
   * @param to
   *          the to
   * @return the state
   */
  protected State transitionTo(State to) {
    if (state.canTransitionTo(to)) {
      State old = state;
      state = to;
      return old;
    } else {
      throw new IllegalStateException("Couldn't transtion from " + state + " to " + to);
    }
  }

  /** The state. */
  volatile private State state = State.DONE;

  /**
   * State.
   *
   * @return the state
   */
  protected State state() {
    return state;
  }

  /** The header. */
  private FrameHeader   header;

  /** The buffer manager. */
  private BufferManager bufferManager = new BufferManager();

  /**
   * Parses the.
   *
   * @param downloadBuffer
   *          the download buffer
   * @return the frame
   * @throws com.taobao.top.link.embedded.websocket.exception.WebSocketException
   *           the web socket exception
   */
  public Frame parse(ByteBuffer downloadBuffer) throws WebSocketException {
    ByteBuffer buffer = null;
    try {
      if (State.DONE.equals(state)) {
        transitionTo(State.HEADER);
        buffer = downloadBuffer;
      } else {
        buffer = bufferManager.getBuffer(downloadBuffer);
      }

      if (State.HEADER.equals(state)) {
        int position = buffer.position();
        header = createFrameHeader(buffer);
        if (header == null) {
          buffer.position(position);
          bufferManager.storeFragmentBuffer(buffer);
          return null;
        }
        if (header.getContentsLength() - 1 > Integer.MAX_VALUE) {
          throw new IllegalArgumentException("large data is not support yet");
        }
        transitionTo(State.FRAME);
      }

      if (State.FRAME.equals(state)) {
        if (header.getContentsLength() > buffer.remaining()) {
          bufferManager.storeFragmentBuffer(buffer);
          return null;
        }

        byte[] bodyBuf = new byte[(int) header.getContentsLength()];
        buffer.get(bodyBuf, 0, bodyBuf.length);
        Frame frame = createFrame(header, bodyBuf);
        transitionTo(State.DONE);
        bufferManager.init();

        header = null;
        return frame;
      }
      return null;
    } finally {
      if (buffer != null && buffer != downloadBuffer) {
        downloadBuffer.position(downloadBuffer.limit() - buffer.remaining());
      }
    }
  }

  /**
   * Creates the frame header.
   *
   * @param chunkData
   *          the chunk data
   * @return the frame header
   */
  abstract protected FrameHeader createFrameHeader(ByteBuffer chunkData);

  /**
   * Creates the frame.
   *
   * @param h
   *          the h
   * @param bodyData
   *          the contents data
   * @return the frame
   */
  abstract protected Frame createFrame(FrameHeader h, byte[] bodyData);
}
